In radio communication systems it is normally necessary for a receiver to determine whether a transmitter is trying to initiate a communication. In such systems where the transmitter is normally active or systems where the air interface includes scheduling information, this issue is readily resolved. However in systems using an asynchronous protocol for communications, determining whether a communication is desired in an efficient manner is still a significant problem. This problem is further exacerbated where the particular frequency for the communications is unknown and by frequency mismatches between the transmitter and receiver, particularly for battery life sensitive applications. The power consumed in monitoring for an asynchronous communication from another device to determine whether an attempt to communicate has occurred may significantly reduce the battery life and thus available service time of the mobile unit. Clearly a method and apparatus are needed for identifying when communications are desired, preferably in a time and power efficient manner given frequency offsets between communications devices.